Antioverheating fuse for spark plugs in internal-combustion engines



o. LARSSON 1,712,221

COMBUSTION ENGINES May 7, 1929.

ANTIOVERHEATING 'FUSE FOR SPARK PLUGS IN INTERNAL Filed March 18 1926 llweldarl U. Larssan,

Patented Ma 7,1929.

UNITED STATES PATENT OFFICE OSCAR LARSSON, or HAESTVED, DENMARK, ASSIGNOR T GEORG HALD, or cornu- HAGEN, DENMARK.

'ANTIOVERHEATING FUSE FOR SPARK PLUGS IN INTERNAL-COMBUSTION ENGINES.

Application filed March 18, 1926. Serial No. 95,761.

Internal combustion engines, in particular such used in automobiles and in ships, can, at times, owing to a discontinuation of the cooling or a reduction or a cessation of the oil-supply become so greatly heated that the pistons seize and stick, or other disturbances in the running of the respective engine occur.

The present invention provides, in order to avoid such trouble, to insert into the electric igniting system a safety fuse which, in .the case of much overheating, will melt and will, thereby, interrupt the electric circuit so that the engine will stop.

The fuse, preferably, consists of a wire or a cartridge of an easily melting metal and is inserted into the circuit of the spark plug, preferably within the spark plug itself. The diameter of such space is greater than the diameter of the fuse and the latter, when melted, therefore reaches a'level lower than the conductor in contact with the top of the fuse, and hence the circuit is .thus interrupted.

In the accompanying drawing the invention is shown by Wayof example.

The figures shows a spark plug in vertical longitudinal section with an anti-overheat -ing-cartridge fitted in the porcelain part. In the drawing the numeral 1 indicates the 'centralporcel'ain bodywith a shoulder 2 locked between the conducting member ,3 and a packing nut 4. The porcelain body 1 has a central channel into the lower end of 35. which a conducting member 5 is fused.

In its upper part this channel is of a larger diameter and here a fuse 6 of easily melting metal is inserted. This fuse bears against the upper end of the conductor 5 while at its top it is in conductive contact with a conductive bar 7 which is, again, conductively connected with the terminal 8.

The current normally flows from the terminal 8 through the bar 7, the fuse 6 the conductor 5 and thence jumps over, to the part 3, which is screwed into the cylinder of the engine and therefore in conductive connection with the latter and the otherpole of the source .of current.

Should, now, .the spark plug become toowarm, either because the cooling fails,-or because the oil supply ceases, the fuse 6 ill melt and fall, thus interrupting the circuit.

-Having now described my invention, what the safety fuse when melted assumes a lower level than the conductor in contact with the top of the fuse, thereby interrupting the circuit. I

In testimony whereof I affix my si nature.

"OSCAR LARssoN. 

